Published: Thu, December 07, 2017
Medicine | By Brett Sutton

Your health: Birth control pills still raise breast cancer risk

Your health: Birth control pills still raise breast cancer risk

Morch's team pored through years of electronic health records collected by the Danish health system, using prescription data to identify which women had taken the drugs and then track their health outcomes.

The study looked at data from 1.8 million women between the ages of 15 and 49 over more than a decade.

These results sound scary at first.

"Gynecologists just assumed that a lower dose of hormone meant a lower risk of cancer".

While contraceptive drugs that contain oestrogen have always been suspected of increasing the likelihood of breast cancer, researchers had expected smaller doses of the hormone, often combined with the drug progestin, would be safer, said Lina Morch, an epidemiologist at Copenhagen University Hospital who led a study analysing the records of 1.8 million women in Denmark. And for those who take the drugs for five years or more, the risk will persist for as long as five years after they stop, she said.

The study also found that the risk increased the longer women used contraceptives involving hormones, suggesting the relationship is causal, Mørch said.

Third-generation contraceptive pills are displayed on January 2, 2013, in Lille, in northern France.

Newer formulations of birth control pills appear the carry the same risk of breast cancer as older versions.


In fact, birth control increases breast cancer risk about as much as drinking alcohol does, said Dr. Mary Beth Terry, an epidemiologist at the Columbia University Mailman School of Public Health.

NEIGHMOND: All of these forms of hormonal contraception increased breast cancer risk by 20 percent.

Those who used them for longer periods were at even greater risk. Dr. Charles A. Leath, a gynecologic oncologist at the University of Alabama at Birmingham, said that while this pathway was plausible, it was far from certain. A 20 percent increase translates into only one extra breast cancer case for almost every 8,000 women.

For some perspective, about 252,710 American women were diagnosed with breast cancer in 2017, according to estimates from the National Institutes of Health; 12.4 percent of women will hear the diagnosis at some point in their lives. But by the time a woman reaches 40, her probability of developing breast cancer in the next 10 years is 1.45 per cent, or 1 in 69.

The paper did not make any note of whether birth control impacted mortality from breast cancer, Leath noted.

It's always been known that hormonal contraception, like any medicine, carries some risks. So this tells us that things haven't changed. Unintended pregnancies cost the US government $21 billion in 2010, according to a report from the Guttmacher Institute.

What really surprised the researchers was that the increased risk was not confined to women using oral contraceptive pills, but also was seen in women using implanted intrauterine devices, or IUDs, that contain the hormone progestin. "As with any medical intervention, hormonal contraception is associated with specific health risks".

Many studies show that oral contraceptives can also reduce the risk for cancer of the ovaries, uterus and possibly the colon.

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